Process for generating a mixed multicomponent vapor for preparation of monoalkyl ethers of diphenols

ABSTRACT

A process and a system thereof include apparatuses for developing multi-component vapor mixture by heating of solution of reactants comprising one or more of diphenols, or diphenol derivatives, and an organic compound. Upon reacting in a vapor state in presence of a catalyst with diphenols, or diphenol derivatives, the organic compound produces a monoalkyl ether of a dihydric phenolic compound. The entire solution of reactants completely transforms into a super-heated multi-component vapor using heaters without the use of thin film evaporator. The complete transformation of the entire solution of the reactants in to super-heated multicomponent vapor is achieved by heating the entire solution firstly by a pre-heater followed by further heating by a super-heater. The unevaporated or condensed high boilers and tar are removed to drain. The superheated vapor is subjected to vapor phase reaction mediated by catalyst to get monoalkyl ether of a dihydric phenolic compound.

FIELD OF INVENTION

This invention pertains to monoalkyl ethers of diphenols. Moreparticularly it pertains to a process for preparation of monoalkylethers of diphenols. Still more particularly it pertains to generating amixed multi-component vapor for preparation of monoalkyl ethers ofdiphenols.

BACKGROUND OF THE INVENTION

One method of preparation of monoalkyl ethers of diphenols comprisesreacting a diphenol or a diphenol derivative such as Catechol,Hydroquinone, Resorcinol, 4-Methyl catechol, 4-Chloro catechol etc. withaliphatic and alicyclic alcohols such as Methanol, ethanol, Isopropylalcohol, Isobutyl alcohol, tert-butyl alcohol, cyclohexanol etc. invapor/gas state in presence of a phosphorus-containing catalyst. In thismethod, achieving a mixed vapor phase of the two reactants in properproportion is a challenging task because the diphenol or a diphenolderivatives have higher boiling point whereas aliphatic and alicyclicalcohols have comparatively lower boiling point. Hence, evaporating asolution of the diphenol or a diphenol derivatives with aliphatic andalicyclic alcohols in conventionally known methods invariably results inhigher proportion of aliphatic and alicyclic alcohols in the resultingtwo-component vapor mixture. Further, if both these components arevaporized independently and then vapors mixed together prior to exposureto catalytic bed, it has been seen that significant degradation of thediphenol or a diphenol derivative occurs.

To achieve efficient conversion of the solution of diphenol or adiphenol derivative and aliphatic and alicyclic alcohols, EP0914854 hasdisclosed an apparatus for generating a mixed multi-component vapor,comprising a thin film evaporator (1) having a feed inlet (1a) throughwhich a mixed multi-component liquid comprising two or more liquidcomponents different in boiling temperature from each other and solublein or compatible with each other is fed into the evaporator and adelivery outlet (1b) through which a resultant mixed multi-componentvapor is delivered from the evaporator; a feed line (2) for feeding themixed multi-component liquid, connected to the feed inlet of theevaporator; a delivery line (5) for delivering the resultant mixedmulti-component vapor, connected to the delivery outlet of theevaporator; and a forcedly liquid-circulating line (3) having acirculation inlet end (3a) connected to a delivery end side portion ofthe evaporator, a circulation outlet end (3b) connected to a feed sideend portion of the evaporator and a liquid transporting means (4)arranged between the circulation inlet end and the circulation outletend of the circulating line, whereby a non-evaporated portion of themixed multi-component liquid is forcedly circulated through thecirculation inlet end, the liquid transporting means and the circulationoutlet end of the circulating line.

EP0914854 has also disclosed a process for generating a mixedmulti-component vapor comprising the steps of: feeding a mixedmulti-component liquid comprising two or more liquid componentsdifferent in boiling temperature from each other and soluble in orcompatible with each other into a feed side end portion of a thin filmevaporator; evaporating the mixed multi-component liquid in theevaporator; and delivering a resultant mixed multi-component vapor froma delivery side end portion of the evaporator, wherein a non-evaporatedportion of the mixed multi-component liquid present in the evaporator isforcedly circulated through a circulating line having a circulationinlet end connected to the delivery side end portion of the evaporator,a circulation outlet end connected to the feed side end portion of theevaporator, and forcedly liquid-transporting means located between thecirculation inlet end and the circulation outlet end of the circulatingline, by withdrawing the non-evaporated portion of the mixedmulti-component liquid from the delivery side end portion of theevaporator through the circulation inlet end and returning the withdrawnnon-evaporated portion of the mixed multi-component liquid into the feedside end portion of the evaporator through the forcedlyliquid-transporting means and the circulation outlet end of thecirculating line, thereby to promote the simultaneous evaporation of thetwo or more liquid components and the generation of a mixedmulti-component vapor in which the two or more components are present insubstantially the same composition as that of the mixed multi-componentliquid.

However, this process and apparatus are capital intensive andinconvenient to operate. A simpler process involving simpleequipment/apparatus was needed.

SUMMARY OF THE INVENTION

This invention comprises a process for developing multi-component vapormixture by heating of solution of reactants comprising one or more ofdiphenols, or diphenol derivatives, and an organic compound, wherein theorganic compound is one which upon reacting in a vapor state in presenceof a catalyst with diphenols, or diphenol derivatives, produces amonoalkyl ether of a dihydric phenolic compound; and wherein the entiresolution of reactants completely transforms into a super-heatedmulti-component vapor using heaters without the use of thin filmevaporator. The complete transformation of the entire solution ofreactants in to super-heated multicomponent vapor is achieved by heatingthe entire solution firstly by a pre-heater followed by further heatingby a super-heater. The process further comprises steps of: (a) removalof the unevaporated or condensed high boilers and tar to drain, and (b)subjecting the superheated vapor to vapor phase reaction mediated bycatalyst to get monoalkyl ether of a dihydric phenolic compound. Theprocess further comprises achieving removal of the unevaporated orcondensed high boilers is in a jacketed vessel which is kept heated byhot oil circulating through the jacket and the super-heated is subjectedto vapor phase catalytic reaction mediated in a vapor phase catalyticreactor containing an Aluminium/Phosphorus catalyst.

This invention also comprises a system for developing multi-componentvapor mixture by heating of solution of reactants comprising one or moreof diphenols, or diphenol derivatives, and an organic compound, whereinthe organic compound is one which upon reacting in a vapor state inpresence of a catalyst with diphenols, or diphenol derivatives, producesa monoalkyl ether of a dihydric phenolic compound; wherein the entiresolution of reactants completely transforms into a super-heatedmulti-component vapor using heaters without the use of thin filmevaporator, the system of claim 9 comprising: a stainless steel reactorunder a nitrogen atmosphere for making a solution of a diphenol or adiphenol derivative in the organic compound at room temperature andheating the same to about 50-50-70° C., a pre-heater to heat thesolution to get vapors and a super-heater to heat the vapors to getsuper-heated vapors multicomponent mixture from the said solution, ajacketed section/vessel (C) for receiving superheated steam at its topand allowing the same from the top end to pass to the vapor phasecatalytic reactor (D) and facilitating separation of condensed highboilers and tar that comes out of super-heater with superheated vaporsto flow down its length over the inner surface of the jacketed sectionwhich is heated by hot oil to a temperature that shall re-evaporate thecondensed high boilers, and allowing negligible quantity of high boilerswhich do not re-evaporate and tars that are formed to be drained outfrom the outlet at the bottom end (8), The system of this inventionfurther comprises multiplicity of tubular reactors arranged in the vaporphase catalytic reactor (D), the tubular reactors being packed withheterogeneous Aluminum/Phosphorus catalyst capable of catalyzing areaction in vapor state between the diphenol/diphenol-derivative and theorganic compound in vapor phase to produce a monoalkyl ether of adihydric phenolic compound to produce a monoalkyl ether of a dihydricphenolic compound in the tubular reactors upon heating to 240-300° C. bycirculating hot oil & kept under Nitrogen atmosphere throughout thecourse of the reaction to achieve the above said reaction, a receiver tocollect cooled and the condensed liquid mass after condensing thereacted vapors, distillation apparatus to separate the methanol & waterfrom above mixture for recycling of un-reacted methanol, a thin-filmevaporator to recover the Guaiacol & Veratrole as a mixture cut wasremoved from the product mass from the high boiling cut of catechol leftin the Thin Film evaporator and recycling the catechol, and a fractionaldistillation set for the separation of Guaiacol & Veratrole underVacuum.

DETAILED DESCRIPTION OF THE INVENTION

Process and apparatus of this invention comprise simpler apparatus andeasier to operate process and yet gives acceptably good conversion toproduct.

It is an embodiment of this invention that the vapor mixture generationwith desired mix of the diphenol or diphenol derivative and aliphaticand alicyclic alcohols is achieved using a pre-heater (A) andSuper-heater (B). It is a further embodiment of this invention thatJacketed section (C) is used to separate and discard the small amount oftar/high boilers that is/are formed. It is also an embodiment of thisinvention that only the super-heated vapor mixture passes to nextreactor to contact the catalyst.

BRIEF DESCRIPTION OF FIGURES AND LEGENDS

FIG. 1: Schematic diagram of process for generating a mixedmulti-component vapor for preparation of monoalkyl ethers of diphenols.

A: Pre-heater, B: Super-heater, C: Jacketed section/vessel, D: Catalyticbed, 1: Feed inlet, 2: Vapor mixture, 3: Superheated vapors, 4:Superheated vapor feed to catalytic bed, 5: Product vapors forseparation, 6: High boilers to drain, 7: Condensed product vapors torecycle, 8: Hot oil inlet to pre-heater, 9: Hot oil outlet frompre-heater, 10: Hot oil inlet to super-heater, 11: Hot oil outlet fromsuper-heater, 12: Hot oil inlet to jacketed section, 13. Hot oil outletfrom jacketed section.

The process scheme consists of mixing a diphenol or diphenol derivativesuch as catechol, Hydroquinone, Resorcinol, 4-Methyl catechol, 4-Chlorocatechol etc. with aliphatic and alicyclic alcohols such as Methanol,ethanol, Isopropyl alcohol, Isobutyl alcohol, tert-butyl alcohol,Cyclohexanol etc. in a mixing vessel at about 40 to 100 deg C. The mixedmulti component liquid is then pumped into feed tank via in-line filterso as to separate any un-dissolved component. The clear multi componentliquid in feed tank is analyzed & adjusted to desired composition byaddition of required component. Preferred composition of themulticomponent liquid comprises one part diphenol or diphenol derivative& 4 parts aliphatic & alicyclic alcohol. The said liquid is thentransferred to pre-heater (A) and heated to a temperature of about 265deg C. to get a vapor that is a multicomponent mixture comprisingdiphenol/diphenol-derivative, aliphatic & alicyclic alcohol. The rate ofintroduction of the multicomponent liquid into the pre-heater (A) andtemperature of the oil circulating through the jacket of the pre-heaterare so set that only the multicomponent vapor that is formed in thepre-heater passes to the section of the super-heater (B). Thismulti-component vapor is further super-heated to a temperature of 285deg C. by super-heater (B) heated by a heating source to get thesuperheated mixed multi component vapors which is delivered at the topof the Jacketed section/vessel (C). At the same time if some of the highboilers escape the process of super heating and condense at the top ofthe jacketed Vessel (C) a part of it would again vaporize due to heatedjacket of (C); and whatever negligible quantity of condensed highboilers that do not vaporize again from the jacket of (C) and the tarsthat are formed during heating process are removed from the bottom asshown in the FIGURE via “High Boilers to drain” (6) so that only vaporsare allowed to pass to next stage. The jacket of (C) is heated by aheating source. The heating source may be hot oil which flows in thejacket through the inlet (12) and comes out through the outlet (13).Temperature of the hot oil is set such that most of the condensed highboilers evaporate again.

The superheated mixed multi component vapors are allowed to pass fromthe top of the vertical externally heated (jacketed) section (c) throughwhich a heating source circulates. The mixed multi component vapors areensured to have same composition as that of the multi-component liquidand the super-heated multi-component vapor is then transferred furtherto the vapor phase catalytic reactor (D).

The non evaporated portion of the mixed multi component liquid isdrained from the bottom of the heated section (6).

The catalyst system used & further manufacturing process used formonoalkyl ether synthesis is as mentioned in WO 01/74485 A1 and themethod of its preparation followed here has been described indescription of the example below. Of course, in place of the catalystsdescribed below, any other catalyst made by any other method thatresults in catalyzing a reaction between vapors of diphenol or diphenolderivative and aliphatic and alicyclic alcohols to make monoalkyl ethersof diphenols can be substituted.

The catalyst used for this process, designated as ALPO catalyst,consists of Mixed oxides of elements such as Phosphorous & Aluminum andis prepared as mentioned in WO 01/74485 A1. In the illustrative process,the Aluminium/Phosphorus catalyst is prepared by a process comprisingfollowing steps: dissolving AlCl₃.6 H₂O in 0.5N HCl with stirring,adding 85% H₃PO₄ to make a clear solution, adding conc. NH₄OH drop-wiseto adjust pH to about 7 to get a precipitate, drying the precipitate tomake a paste, drying the paste further to obtain dry white mass,treating the dried mass in air stream at high temperature, subjectingthe solid to compression, granulation & sieving to obtain granulescontaining the Aluminum/Phosphorus analytic ratio in the final catalystas 0.064±0.04, forming the catalyst into square shapes, mixing thecatalyst with binder and Polyvinyl Acetate (PVA) Powder in a kneader,slowly adding distilled water & continuing kneading of the mass so as toform a dough of a consistency similar to that required for bread making,pressing the dough to convert it in noodles shape, slowly drying thesenoodles until constant weight is achieved, grinding these noodles &passing through a sieve so as to convert it in fine powder, passing thepowder through tabletting/pelleting machine so as to convert it insquare shape, calcining the square shaped catalyst in Nitrogenatmosphere before using it for reaction. Details are given in theexamples described below.

This invention may also be used for developing multi-component vapormixture for reacting with each other in a catalytic reaction forpreparation of producing a monoalkyl ether of a dihydric phenoliccompound; the components of the vapor mixture comprising high boileraromatic compounds having one or more hydroxyl group including, withoutlimitation, phenol, guaiacol, catechol, hydroquinone, resorcinol,2-methyl catechol, 4-methyl catechol, 2-methyl hydroquinone,2-chlorocatechol and 4-chlorocatechol; and low boiling organiccompounds, which, upon reacting in a vapor state in presence of acatalyst with diphenols, or diphenol derivatives, produces a monoalkylether of a dihydric phenolic compound, the organic compound including,without limitation, aliphatic alcohols, cycloaliphatic alcohols,aliphatic ethers, aliphatic ketones, aliphatic glycols, aliphaticcarboxylic acid esters, aliphatic hydrocarbons, cycloaliphatichydrocarbons, aromatic hydrocarbons and water, each having a boilingtemperature of 50 to 200.degree. C.

In one embodiment of the invention, the process of this inventioncomprising steps described below. A diphenol or diphenol derivative ismixed with an aliphatic or alicyclic alcohol. The aliphatic or alicyclicalcohol may comprise, without limitation, Methanol, ethanol, Isopropylalcohol, Isobutyl alcohol, tert-butyl alcohol, n-butyl alcohol, isoamylalcohol, Amyl alcohol, 2-Methyl butan-1-ol, Neopentylalcohol,3-pentanol, Methyl propyl carbinol, Methyl propyl isocarbinol,Tertiary amyl alcohol, cyclohexanol, cyclopentanol, cyclobutanol, andcyclopropanol. The reactants may be taken in a mixing vessel at about 40to 100 deg C., un-dissolved components filtered out, the clear multicomponent liquid in feed tank analyzed and the same is adjusted to thedesired composition by addition of required component, Themulti-component liquid is transferred to pre-heater (A) and super-heater(B) which are heated by a heating source to get the superheated mixedmulti component vapors from top of the Jacketed vessel (C). If some ofthe high boilers escape the process of super heating and condense, theyare removed from the bottom of the jacketed vessel via “High Boilers todrain” so that only vapors are allowed to pass to next stage allowingthe superheated mixed multi component vapors to pass through a verticalexternally heated (jacketed) section (c) through which hot oil goes inthrough the inlet (12) and comes out through outlet (13), heating theheated section to ensure the complete evaporation of the high boilingcomponent of the mixed multi component liquid, ensuring that the mixedmulti component vapors have same composition as that of themulti-component liquid. The the non evaporated portion of the mixedmulti component liquid is drained off from the bottom of the heatedsection (6),

In particular example of working of this invention, catechol andmethanol are charged to a Stainless Steel reactor of 4000 L capacity.The ratio between catechol and methanol may range between 1:20 moles to1:2 moles. This ratio may more preferably be 1:5 moles. The mixing isdone at room temperature under Nitrogen atmosphere. Heating is startedto raise the temperature to about 50-70° C. until a clear hot solutionof catechol in methanol is formed, the hot solution of Catechol inMethanol is passed through a pre-heater & a super-heater so as to get amulticomponent vapor mixture containing catechol and methanol, which iscollected from the jacketed column (C) and fed at the rate of 250 L to300 L/hr through the tubular reactor catalyst bed (D). The rate ofpassage of the multicomponent mixture may vary depending on thedimensions of various equipment in this series and also of the number oftubular reactors and their capacities.

The Multiple tubular Reactor used in the illustration contained 146tubes, each tube having length of 1000 to 1500 cm & diameter 72 cm.These dimensions may be varied as needed. The tubes are filled withheterogeneous Aluminum/Phosphorus catalyst. Usually 100 kg-500 kg, ofthe catalyst is used in cube form of size 2 mm×2 mm prepared asdescribed above and in the example. The tubular reactor/s is/are heatedto 240-300° C. by circulating hot oil & kept under Nitrogen atmospherethroughout the course of the reaction, The reaction temperature ismaintained within a range of 240-300° C. during this operation so as tokeep the reactants in vapor state during the reaction with the catalyst,Thereafter, the vapors are cooled and the condensed liquid masscomprising Guaiacol, Veratrole, Catechol, water and unreacted methanolis collected in a receiver, The methanol and water are removed fromabove mixture, Methanol is recycled back to step I and water isdiscarded, The Guaiacol & Veratrole mixture cut is removed from theproduct mass through use of Thin Film evaporator (TFE) & the highboiling cut of Catechol left in the TFE is recycled.

The separation of Guaiacol & Veratrole may be achieved by fractionaldistillation. It is convenient to use a 1000 to 1500 cm packed column(d=60-70 cm) & under Vacuum to get Guaiacol having purity of about99.75-99.85% and Veratrole—0.2-0.3% with a yield of 50-65%, Residualmass consisting of mainly Catechol having purity of 97-99% is sentwithout any distillation for recycle in the reaction.

The polymeric tars generated through continuous operation are eliminatedfrom bottom of the reactor (8) as high boilers once in every 4 hoursoperation.

In the following is described an illustrative example of this invention.The example is intended only as an illustration and does not limit thescope of the invention by any means by the specific reactants used andspecific reaction conditions used. Variations from this example that areobvious to a person skilled in the art and obvious equivalents areconsidered to be within the scope of this invention.

Example 1

In a SS (Stainless Steel) reactor 4000 L capacity Catechol & Methanolwas charged in a ratio 1:20 to 1:2 moles. The ratio may be 1:10;preferably 1:5 and mixing may be done at room temperature under Nitrogenatmosphere. Heating was started to raise the temperature to about 50-70°C. until a clear solution is formed.

In a Multiple tubular Reactor containing 146 tubes, the tubes werefilled with heterogeneous ALPO catalyst (100 kg-500 kg.) in cube form ofsize 2 mm×2 mm prepared as per example 2 of WO 01/74485 A1 and asdescribed below under title: “Preparation of catalyst”.

The length of each tube was 1000 to 1500 cm & diameter 72 cm. Thisdimension of the tubes is illustrative; and may be varied as perrequirement. The tubular reactor was heated to 240-300° C. bycirculating hot oil & kept under Nitrogen atmosphere throughout thecourse of the reaction.

The Catechol+Methanol hot solution (prepared as above) was passedthrough a pre-heaters & a super-heater as described previously so as toeliminate any material in solid or liquid state. The vapors so formedare collected from (C) & fed at the rate of 250 L to 300 L/hr throughthe tubular reactor catalyst bed D. Te catalyst was prepared asdescribed further below.

The reaction temperature is maintained within a range of 240-300 deg C.during this operation so as to keep the reactants in vapor state duringthe reaction with the catalyst.

Thereafter, the vapors are cooled and the condensed liquid mass is thencollected in a receiver. The typical content of this solution is asfollows: Guaiacol—50-60%, Veratrole—1.2%, Catechol—40-50% along withun-reacted Methanol & water formed in the reaction. The methanol & waterwas removed from above mixture. Separation of the methanol and water isdone in the illustrative example by distillation. Methanol was recycledback to step I and water was discarded.

The Guaiacol & Veratrole Mixture cut was removed from the product massthrough use of Thin Film evaporator (TFE) & the high boiling cut ofCatechol left in the TFE was recycled.

The separation of Guaiacol & Veratrole was achieved by fractionaldistillation using 1000 to 1500 cm packed column (d=60-70 cm) & underVacuum. Purity of Guaiacol—99.75-99.85% & Veratrole—0.2-0.3%. Yield50-65%. Residual mass consisting of mainly Catechol was sent to Step Iwithout any distillation for reaction. Purity of Catechol was 97-99%.The polymeric tars generated through continuous operation was eliminatedfrom bottom of the reactor (8) as high boilers once in every 4 hoursoperation.

Preparation of Catalyst

59.2 g of AlCl₃.6 H₂O were dissolved in 200 ml of 0.5N HCl (190 mlH₂O+10 ml of 37% HCl) with stirring. 21 ml of 85% H₃PO₄ by weight aresubsequently added. To the clear solution was then added drop-wise conc.NH₄OH (about 90 ml) to adjust pH to about 7. The formed precipitate wassubsequently dried by suction on a filter to obtain a paste. The pastewas then dried in a static dryer at 120° C. for 12 hours to obtain whitemass, which was then treated in air stream at high temp, using followingtime table as follows: from room temp to 300° C. at 10°/min rate,keeping the temp of 300° C. for 4 hours, subsequent heating from 300 to600° C. at 10°/min rate, keeping the temp. of 600° C. for 4 hours. Thesurface area of the resulting sample was 74±5 m²/g. The solid was thensubjected to compression, granulation & sieving to obtain granuleshaving average size ranging from 0.5 to 1 mm. The Aluminum/Phosphorusanalytic ratio in the final catalyst determined by plasma spectrometry,was 0.064±0.04. The catalyst was then extruded into cube shapes of 2mm×2 mm by using standard methods as mentioned in the literature.

175 gm of this catalyst was mixed with 37.5 gm of binder (Kaolin orBentonite clay procured from local supplier) & 37.5 gm of PolyvinylAcetate (PVA) Powder in a sigma kneader. To this mixture was slowlyadded 210 ml of distilled water & kneading of mass continued so as toform a dough of a consistency similar to that required for bread making.This dough is then pressed in a mill so as to convert it in noodlesshape. These noodles were slowly dried in a dryer at 100 deg C. untilconstant weight is achieved. Total time required for drying is about 8hours. Weight of dried product—240 gm.

These noodles are then ground & passed through a 100 mesh sieve so as toconvert it in fine powder. This powder is then passed throughtabletting/pelleting machine so as to convert it in square shape of size2 mm×2 mm. This square shaped catalyst has good hardness & strength. Itis calcined at about 560 deg C. temperature for 4 hours in Nitrogenatmosphere before using it for reaction.

We claim:
 1. A system for developing multi-component vapor mixture byheating of solution of reactants comprising one or more of diphenols, ordiphenol derivatives, and an organic compound, wherein the organiccompound is one which upon reacting in a vapor state in presence of acatalyst with diphenols, or diphenol derivatives, produces a monoalkylether of a dihydric phenolic compound; wherein the entire solution ofreactants completely transforms into a super-heated multi-componentvapor using heaters without the use of thin film evaporator.
 2. Thesystem of claim 1 comprising: a. a stainless steel reactor under anitrogen atmosphere for making a solution of a diphenol or a diphenolderivative in the organic compound at room temperature and heating thesame to about 50-50-70° C., b. a pre-heater to heat the solution to getvapors and a super-heater to heat the vapors to get super-heated vaporsmulticomponent mixture from the said solution, c. a jacketedsection/vessel for receiving superheated steam at its top and allowingthe same from the top end to pass to the vapor phase catalytic reactorand facilitating separation of condensed high boilers and tar that comesout of super-heater with superheated vapors to flow down its length overthe inner surface of the jacketed section which is heated by hot oil toa temperature that shall re-evaporate the condensed high boilers, andallowing negligible quantity of high boilers which do not re-evaporateand tars that are formed to be drained out from the outlet at the bottomend,
 3. The system of claim 2 further comprising: a. Multiplicity oftubular reactors arranged in the vapor phase catalytic reactor, thetubular reactors being packed with heterogeneous Aluminum/Phosphoruscatalyst capable of catalyzing a reaction in vapor state between thediphenol/diphenol-derivative and the organic compound in vapor phase toproduce a monoalkyl ether of a dihydric phenolic compound to produce amonoalkyl ether of a dihydric phenolic compound in the tubular reactorsupon heating to 240-300° C. by circulating hot oil & kept under Nitrogenatmosphere throughout the course of the reaction to achieve the abovesaid reaction, b. a receiver to collect cooled and the condensed liquidmass after condensing the reacted vapors, c. disytillaiton apparatus toseparate the methanol & water from above mixture for recycling ofun-reacted methanol, d. a thin-film evaporator to recover the Guaiacol &Veratrole as a mixture cut was removed from the product mass from thehigh boiling cut of catechol left in the Thin Film evaporator andrecycling the catechol, e. a fractional distillation set for theseparation of Guaiacol & Veratrole under Vacuum.